Roughly a third of women in their child-bearing years are using prescription painkillers, according to a new study out of the Centers for Disease Control and Prevention. It's a statistic that worries health experts, as it greatly increases the likelihood that these women will use the medications while pregnant, potentially doing harm to their unborn children.

According to the report -- which looked at data on women 15 to 44 years from 2008 to 2012 -- an average of 39 percent of women on Medicaid and 28 percent of women with private insurance filled out a prescription for opioid painkillers each year.

Opioids are typically prescribed to treat moderate to severe pain. Though experts said there's a dearth of research on the potential risks on opioids to unborn children, there are indications that the medications can be harmful.

Studies have shown that using the prescription medications in pregnancy might increase the risk of major defects of the baby's brain and spine, as well as congenital heart defects and defects in the baby's abdominal wall.

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Fast factsHere are some quick facts on painkiller use in reproductive aged women, from the Centers for Disease Control and Prevention.Researchers analyzed data from 2008 to 2012 on women 15 to 44 years old.They found that an average 39 percent of women enrolled in Medicaid filled a prescription for opioid medications annually.An average 28 percent of women with private health insurance filled painkiller prescriptions each year.The most commonly prescribed opioids in both groups were hydrocodone, codeine and oxycodone

Exposing unborn children to opioids also increases the risk of neonatal abstinence syndrome, in which a newborn experiences symptoms of withdrawal from medications or drugs taken by a mother during pregnancy.

Babies may also feel the effects of withdrawal while still in the womb, said Dr. John Douglas, clinical director of the Outpatient Opioid Addiction Program at Silver Hill Hospital in New Canaan.

Opioid painkillers are highly addictive, and Douglas said the trauma of a woman repeatedly quitting and getting back on the medication while pregnant can be brutal on an unborn baby. He said this cycle of rehabilitation and relapse can increase the risk of premature birth, bleeding and even the loss of the child.

If a woman addicted to painkillers is pregnant, Douglas said, she needs to know immediately so that doctors can put her on some sort of opioid maintenance, using the medication methadone. Methadone is an opioid typically used to reduce withdrawal symptoms in those addicted to heroin.

Though it seems counterinituitive, Douglas said, "that is shown to be safer to the fetus than having the women stop opioids."

According to the CDC's research, the most commonly prescribed opioids were hydrocodone, codeine and oxycodone.

The study also showed that opioid prescription rates were highest among women in the South and lowest in the Northeast, and that white women were one and half times more likely to be prescribed the medications than black or Hispanic women.

Richards said one point the study drives home is that women in their childbearing years -- even those not planning to get pregnant -- need to be careful about what they put in their bodies, just to be safe.

"Any medication a reproductive-aged woman takes should be coupled with counseling from the prescribing doctor," she said.